Functional analysis of cis-regulatory elements within the promoter of the tobacco late pollen gene g10
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The tobacco gene g10 is preferentially and maximally expressed in mature pollen, shows homology to pectate lyases, and is the putative homologue of the tomato gene lat56. Analysis of regulatory elements within the g10 promoter was carried out to verify the importance of putative regulatory sequence motifs. Analysis of transgenic plants showed that 1190 bp of g10 5′ sequence directed preferential expression of GUS in pollen, with bimodal peaks of expression just before and during pollen mitosis I, and in mature anthers. This was confirmed by northern analysis of native g10 transcripts in isolated spores. Transient expression analysis defined the minimal g10 promoter region capable of directing expression in pollen as −86 to +217. Three upstream regions within −427 bp modulate the expression from g10. Gain-of-function analyses showed that the region from −106 to −53 could enhance pollen-specific expression of a minimal CaMV 35S promoter. These analyses further showed that sequences upstream of −86 modulate expression in pollen, but are not essential for preferential pollen expression. The function of a conserved GTGA motif shared between the tobacco g10 and tomato lat56 promoters was demonstrated in g10. Thus, further functional evidence is provided for the conservation of mechanisms for the regulation of late pollen genes across species.
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